Apparatus for producing doubly oriented single crystal castings

ABSTRACT

An apparatus to produce single crystal parts in which the orientation of the dendrite growth in two planes at right angles to one another is described. In effect this produces an orientation in all three right-angle planes of the cast article.

United States Patent Inventors Bernard H. Kear Maison, Cum; Larry W. Sink, Milwaukee, Oreg. Appl. No. 806,869 Filed Mar. 13, I969 Patented Aug. 10, 1971 Aaignee United Aircraft Corporation Est lhrtlord, Coll.

APPARATUS I'Ol PRODUCING DOUBLY ORIENTED SINGLE CRYSTAL CASTINGS s Chi-a, 4 nnwh; Ike.

[50] Field of Search 164/60, 122, 125, 127, 338, 353, 361

[56] References Cited UNITED STATES PATENTS 3,342,455 9/1967 Fleck et al. 253/77 3,485,291 12/1969 Piearcey 164/127 3,515,205 6/ 1970 Wickstrand 164/353 Primary Examiner-J. Spencer Overholser Assistant Examiner-John E. Roethel Attorney-Charles A. Warren ABSTRACT: An apparatus to produce single crystal parts in which the orientation of the dendrite growth in two planes at right angles to one another is described. In effect this produces an orientation in all three right-angle planes of the cast article.

PATENTED ms 3 0 new INVENTORS LARRY W. SIN K BERNARD H. KEAR FIG. 3

ATTORNEY APPARATUS FOR PRODUCING DOUBLY ORIENTED SINGLE CRYSTAL CASTINGS BACKGROUND THE INVENTION The Piearcey U.S. Pat. No. 3,494,709 describes the casting of single crystal parts in which the dendrite growth is oriented with respect to the longitudinal axis of the cast part. However, for certain devices, a more precise orientation of thedendrites in a plane at right angles to the longitudinal axis may be essential and may'produce, in some particularly stressed parts'a superior strength, since the strength of the single crystal castings varies in accordance with the orientation of the dendrites.

SUMMARY OF INVENTION One feature of the invention is an apparatus by which to selectively orient the dendrite growth and thus the strength characteristics in a particular relation to the patt in each of two directions, that is to say, in both a vertical and a horizontal direction with respect to the part as cast. Another feature is a method by which this orientation may be obtained.

A principal object of the invention is the production of single crystal castings in which the crystalline orientation, the dendrite growth is selectively oriented in each of two directions at right angles to one another.

In accordance with the invention, the casting is rhade in a mold having associated therewith a pair of chill plate surfaces at right angles to one another to establish columnar grain growth perpendicularly to each chill surface. The intersecting grain growths produce a vertical grain growth in which the dendritic growth is positioned at right angles to both chill surfaces and thus doubly oriented. From this doubly oriented growth a single crystal is selected to grow into the effective mold portion.

Other features and advantages will be apparent from the specification and claims; and from the accompanying drawings which illustrate an embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical sectional view through a device embodying the invention.

FIG. 2 is a transverse sectional view along line 2-2 of FIG. 1.

FIG. 3 is a greatly enlarged diagrammatic view of a vertical section of a doubly oriented single crystal casting.

FIG. 4 is an enlarged diagrammatic view of a horizontal section of the same single crystal casting.

DESCRIPTION OF THE PREFERRED EMBODIMENT The doubleoriented casting is made in a ceramic tube mounted on a box 12 constituting a chill. The latter has a' cooled bottom surface 14, and cooled side surfaces 16 and 18 at right angles to one another and at right angles to the bottom surface. These surfaces are the inner surfaces of the bottom wall 20 and sidewalls 22 and 24 of the box all of which are cooled by cooling coils 26 embedded therein or in contact with the outer surfaces. These walls thus form chill plates for cooling the metal in contact therewith. The tube 10 has a flange 28 adjacent but spaced from the lower end and this flange serves to support the tube on the box 12.

The tube is surrounded by a plurality of axially alignedzheating coils 30, preferably induction heating coils, and these may be separately controlled for establishing the desired temperature gradient in the tube as described in the Lyons U.S. Pat. No. 3,346,039. Within the tube I0 are secured individual atticle molds 32 and 34 in which the doubly oriented articles are cast. Each mold has a restricted opening 36 at the bottom which is of a size to permit the entry of a single crystal of the plurality of columnar grains growing in the tube, as will be later described. I

In use, the tube 10 and the molds therein are-heated by the surrounding coils to a temperature above the melting point of the alloy to be cast. Water is then circulated through the cooling coils for the chill plate and the alloy is poured into the tube. As the alloy fills the box 12 and the tube 10 it also fills the molds 32 and 34 but is kept molten within the tube and molds by reason ofth'e temperature of these parts.

Crystallization begins at the chill plates as soon as the alloy comes in contact with the chill surfaces and directional solidification begins with the columnar structure perpendicular to each chill surface as described in a VerSnyder U.S. Pat. No. 3,260,505. The dendri tic growth in these columns is also at right angles to the chill surfaces from which the columnar growth extends so that dendritic growth is oriented in directions at right angles to each of the several chill surfaces. The downwardly extending lower end of the tube 10 serves as a baffie to prevent misoriented grains which may nucleate from the top of the chill from entering the inside of the tube.

The grains from the side chill surfaces and the grains from the bottom surface intersect and cause vertical heat flow through the horizontally oriented columnar grains and, with the resultant fast vertical cooling a doubly oriented close columnar grain structure then grows upward within the tube toward the molds. The small opening in the bottom of each mold selects a single doubly oriented grain to grow in each mold, the single grain functioning in effect as a single seed crystal. By close control of the temperature gradient within K the tube, the solidification of the alloy in the tube and in the mold will occ in each tnold.

Other shapes of chill cavities may be used and an orientation of the chill surfaces differently with respect to the longitudinal axis of the tube may serve to control the orientation of the crystalline structure within each mold. Thus, if the tube extends at an acute angle to the horizontal chill surface the dendrites will have the same acute angle in the crystal in each mold.

Where the mold has a small opening at the lower end, as above described, it will be apparent that the mold may be relatively large with respect to the tube as the mold will fill from the top as soon as the tube is filled to a point above the top of the mold. The control of the temperature gradient within the tube by controlling the energy supply to the several coils, thereby to produce the desired fast solidification rate from the bottom to the top of the tube with the liquid-solid interface remaining basically horizontal during the solidification, is well known as described, for example, in VerSnyder U.S. Pat. No. 3,260,505, or Lyons U.S. Pat. No. 3,346,039.

We claim:

1. Apparatus for casting a doubly oriented single crystal article including a grain orientation cavity, and an article mold above said cavity having a restricted passage communicating from said cavity to said mold, in combination with a air of chill plates one of which forms the bottom wall of the cavity ur at such a rate 'a's' to produce single crystal parts ar ld the other of which forms one of the sidewalls of said cavity, said sidewall plate being laterally offset from the restricted passage, said plates having their cavity exposed surfaces substantially at right angles to one another, whereby oriented columnar growth occurs in the cavity at right angles to each plate and thereby establishing both vertical and horizontal orientations of dendritic growth in the mold, and means for cooling each chill plate and for heating and controlling the temperature of the mold.

2. Apparatus for casting a doubly oriented single crystal ar-' ticle as in claim I in which the longitudinal axis of the mold is spaced frd'tn the sleeve and defining the bottom wall of the l crystal selecting passage at the lower end to select a single crystal from the grain growth within the sleeve, said passage terminating above the lower end of the sleeve.

5. Apparatus as in claim 3 in which the sleeve is surrounded by a plurality of spaced heating coils to establish a thermal gradient in the sleeve during solidification of the alloy being cast.

Win50 UNITED STATES PATENT OFFICE QERTIFICATE OF CORRECTIGN Patent No. 3,598,176 Dated August 10, 197].

Inventor(s) Bernard H. Kear and Larry W. Sink It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Add to Figure 1 the reference numerals 32 and 34 to indicate the article moles on the right side and left side respectively within the tube 10 and the reference numerals 36 at the bottom of each of said molds to indicate the restricted openings therein.

Signed and sealed this 25th day of April 1972,

(SEAL) tte s t:

EDWARD Z LFLEI'CHEFQJR. ROBERT GOTTSCHA'LK A; aestl vi; 1 1C6]? Commissioner of Patents 

2. Apparatus for casting a doubly oriented single crystal article as in claim 1 in which the longitudinal axis of the mold is positioned at a selected angle with respect to the horizontal chill plate in order to obtain the desired orientation of the dendritic growth in the mold.
 3. Apparatus for producing doubly oriented single crystal parts including, a casting sleeve an article mold within said sleeve and having a crystal selecting passage at the bottom, a chill cavity at the base of the sleeve having a plurality of chill plates oriented at right angles to one another in said cavity, one of said plates being substantially horizontal and below and spaced from the sleeve and defining the bottom wall of the cavity and another of said plates being substantially vertical and defining one sidewall of the cavity, said vertical plate being offset laterally from the casting sleeve and at least in part below the lower end of the sleeve, thereby to produce both vertical and horizontal orientation of the dendritic growth within the sleeve.
 4. Apparatus as in claim 3 in which a plurality of individual article molds are positioned within the casting sleeve with a crystal selecting passage at the lower end to select a single crystal from the grain growth within the sleeve, said passage terminating above the lower end of the sleeve.
 5. Apparatus as in claim 3 in which the sleeve is surrounded by a plurality of spaced heating coils to establish a thermal gradient in the sleeve during solidification of the alloy being cast. 